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United States Patent |
6,106,957
|
Fang
|
August 22, 2000
|
Metal-matrix diamond or cubic boron nitride composites
Abstract
A metal-matrix diamond or cubic boron nitride composite and method of
making the same are disclosed. The metal-matrix/diamond composite includes
grains of diamond uniformly distributed in a metal matrix. Alternatively,
grains of cubic boron nitride may be used. Suitable metals for the metal
matrix material may include nickel, cobalt, iron, and mixtures or alloys
thereof. Other transition metals also may be used. The
metal-matrix/diamond or metal-matrix/cubic boron nitride composite has
high fracture toughness due to its fine microstructure. Such a
metal-matrix/diamond or metal-matrix/cubic boron nitride composite is
suitable for use in blanks or cutting elements for cutting tools, drill
bits, dressing tools, and wear parts. It also may be used to make wire
drawing dies.
Inventors:
|
Fang; Zhigang (The Woodlands, TX)
|
Assignee:
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Smith International, Inc. (Houston, TX)
|
Appl. No.:
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266111 |
Filed:
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March 10, 1999 |
Current U.S. Class: |
428/545; 75/243; 75/244; 75/245; 75/246 |
Intern'l Class: |
B22F 003/00 |
Field of Search: |
75/245,246,244
428/545
419/16,23,32,35
|
References Cited
U.S. Patent Documents
4151686 | May., 1979 | Lee et al. | 51/307.
|
4234048 | Nov., 1980 | Rowley | 175/329.
|
4428906 | Jan., 1984 | Rozmus | 419/48.
|
4656002 | Apr., 1987 | Lizenby et al. | 419/10.
|
4695321 | Sep., 1987 | Akashi et al. | 75/243.
|
4744943 | May., 1988 | Timm | 419/10.
|
4749545 | Jun., 1988 | Begg et al. | 419/13.
|
4931068 | Jun., 1990 | Dismukes et al. | 51/293.
|
5096465 | Mar., 1992 | Chen et al. | 51/295.
|
5120495 | Jun., 1992 | Supan et al. | 419/11.
|
5130771 | Jul., 1992 | Burnham et al. | 357/81.
|
5451352 | Sep., 1995 | Cook | 264/102.
|
5589268 | Dec., 1996 | Kelley et al. | 428/408.
|
Foreign Patent Documents |
0 181 979 A1 | May., 1986 | EP.
| |
0 352 811 A1 | Jan., 1990 | EP.
| |
10071569 | Mar., 1998 | JP.
| |
WO 92/07102 | Apr., 1992 | WO.
| |
Other References
P. Price, "Hot Isostatic Pressing of Metal Powders"; Metals Handbook Ninth
Edition, vol. 7, Powder Metallurgy; pp. 419-443; 1984.
C. Kelto, "Rapid Omnidirectional Compaction"; Metals Handbook Ninth
Edition, vol. 7, Powder Metallurgy; pp. 542-546; 1984.
R. Dotter, "Blending and Premixing of Metal Powders"; Metals Handbook Ninth
Edition, vol. 7, Powder Metallurgy; pp. 186-189; 1984.
PCT International Search Report, Jun. 8, 1999, 2 pages.
|
Primary Examiner: Mai; Ngoclan
Attorney, Agent or Firm: Rosenthal & Osha L.L.P.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority from the provisional application entitled
"Metal-Matrix Diamond or Cubic Boron Nitride Composites" (Ser. No.
60/078,553) filed on Mar. 19, 1998.
Claims
What is claimed is:
1. A super-hard composite material comprising:
a super-hard component representing about 40%-85% of the volume of the
super-hard material;
a metal matrix component representing about 15%-60% of the volume of the
super-hard material, the metal matrix component selected from the group of
nickel, iron, cobalt, molybdenum, tungsten, niobium, tantalum, vanadium
and alloys thereof; and
wherein the super-hard component and the metal matrix component are
combined in a uniform composite mixture with an actual density at least
95% of the theoretical maximum density of the composite mixture.
2. The super-hard composite material of claim 1 wherein the super-hard
component is cubic boron nitride.
3. The super-hard composite material of claim 1 wherein the super-hard
component is diamond.
4. The super-hard composite material of claim 3 wherein the diamond is
natural.
5. The super-hard composite material of claim 3 wherein the diamond is
synthetic.
6. The super-hard composite material of claim 1 wherein the size of grains
of the super-hard component is between 1 .mu.m and 30 .mu.m.
7. The super-hard composite material of claim 1 wherein the super-hard
component is coated with a layer of metal different from the metal matrix
component.
8. The super-hard composite material of claim 7 wherein the metal in the
layer of metal is selected from the group consisting of copper, titanium
nitride, titanium carbonitride, zirconium nitride, cobalt, tungsten, and
nickel.
9. The super-hard material of claim 1 wherein the size of grains of the
metal matrix component is between 1 .mu.m and 30 .mu.m.
10. A super-hard composite material comprising:
a super-hard component representing about 40%-85% of the volume of the
super-hard material;
a metal matrix component representing about 15%-60% of the volume of the
super-hard material, the metal matrix component selected from the group of
nickel, iron, cobalt, molybdenum, tungsten, niobium, tantalum, vanadium
and alloys thereof; and
wherein the super-hard component and the metal matrix component are
combined in a uniform composite mixture under cold compression so as to
have an actual density at least 95% of the theoretical maximum density of
the composite mixture.
11. The super-hard composite material as defined in claim 10 wherein the
super-hard component comprises cubic boron nitride.
12. The super-hard composite material as defined in claim 10 wherein the
super-hard component comprises diamond.
13. The super-hard composite material as defined in claim 10 wherein the
super-hard component comprises grains having a size between 1 micrometer
and 30 micrometers.
14. The super-hard composite material as defined in claim 10 wherein grains
of the super-hard component are coated with a metal different from the
metal forming the metal matrix component.
15. The super-hard composite material as defined in claim 14 wherein the
metal coating the grains of the super-hard material is selected from the
group of nickel, iron, cobalt, molybdenum, tungsten, niobium, tantalum,
vanadium and alloys thereof.
16. A super-hard composite material comprising:
a super-hard component representing about 40%-85% of the volume of the
super-hard material;
a metal matrix component representing about 15%-60% of the volume of the
super-hard material, the metal matrix component selected from the group of
nickel, iron, cobalt, molybdenum, tungsten, niobium, tantalum, vanadium
and alloys thereof; and
wherein the super-hard component and the metal matrix component are
combined in a uniform composite mixture so as to have an actual density at
least 95% of the theoretical maximum density of the composite mixture, and
wherein particles of said super-hard component are substantially separated
from each other by particles of said metal matrix component.
17. The super-hard composite material as defined in claim 16 wherein the
super-hard component comprises cubic boron nitride.
18. The super-hard composite material as defined in claim 16 wherein the
super-hard component comprises diamond.
19. The super-hard composite material as defined in claim 16 wherein the
super-hard component comprises grains having a size between 1 micrometer
and 30 micrometers.
20. The super-hard composite material as defined in claim 16 wherein grains
of the super-hard component are coated with a metal different from the
metal forming the metal matrix component.
21. The super-hard composite material as defined in claim 20 wherein the
metal coating the grains of the super-hard material is selected from the
group of nickel, iron, cobalt, molybdenum, tungsten, niobium, tantalum,
vanadium and alloys thereof.
Description
FIELD OF INVENTION
The invention relates to wear resistant materials and more particularly to
diamond-based materials for manufacturing cutting elements for use in
cutting and drilling applications.
BACKGROUND
Super-hard materials, such as diamond or cubic boron nitride (CBN), have
superior wear resistance and are commonly used as cutting elements for
cutting or drilling applications. In these applications, a compact of
polycrystalline diamond or CBN is commonly bonded to a substrate material
(e.g., cemented metal carbide) to form a cutting structure. A compact is a
polycrystalline mass of super-hard particles, such as diamond or CBN, that
are bonded together to form an integral, tough, coherent, and
high-strength mass. The substrate material generally is selected from the
group consisting of tungsten carbide, titanium carbide, tantalum carbide,
and mixtures thereof. The substrate material further contains a
metal-bonding material selected from the group consisting of cobalt,
nickel, iron, and mixtures thereof. The metal bonding material is normally
6 to 25 percent of the material by weight. Such compacts and other
super-hard structures have been used as blanks for cutting tools, drill
bits, dressing tools, wear parts, and rock bits. Additionally, compacts
made in a cylindrical configuration have been used to make wire drawing
dies.
Various methods have been developed to make polycrystalline diamond or CBN
compacts. One such method involves subjecting a mass of separate crystals
of the super-hard abrasive material and a catalyst metal to a high
pressure and high temperature (HPHT) process which results in
inter-crystal bonding between adjacent crystal grains. The diamond or CBN
materials are thermodynamically stable under the pressure and temperature
conditions used in HPHT. The catalyst metal may be a cemented metal
carbide or carbide-molding powder. A cementing agent also may be used that
acts as a catalyst or solvent for diamond or CBN crystal growth. The
cementing agent generally has been selected from cobalt, nickel, and iron
when diamonds are used as the super-hard abrasive material. Aluminum or an
aluminum alloy generally is used as a cementing agent when CBN is used as
the super-hard material. The catalyst metal preferably is mixed with the
super-hard crystals (e.g., in powder form).
Although the catalyst may be mixed in powder form with the super-hard
crystals, no attempt is made to minimize the formation of clusters of
super-hard crystals. As a result, the compacts produced by this method
commonly are characterized by diamond-to-diamond or CBN-to-CBN bonding
(i.e., inter-crystal bonding between adjacent grains). This maximization
of inter-crystal bonding between adjacent grains is an objective in making
super-hard compacts. Typically, a diamond compact formed in the presence
of cobalt contains multiple clusters of diamond grains with each cluster
containing more than one (e.g., 3 to 6) diamond grains. These clusters
connect with each other and form a network of diamond grains. In a typical
diamond compact, diamond grain-to-grain contiguity is greater than 40%.
The diamond grain-to-grain contiguity refers to the percentage of
continuous diamond phase in a given direction within a diamond compact,
and is indicative of the extent of diamond-diamond contact in the diamond
compact. The cobalt phase typically is not a continuous matrix. Instead,
pools of cobalt are distributed in the spaces formed by the diamond
clusters. The average size of the cobalt pools typically is larger than
the average size of the diamond grains.
With this microstructure, the compacts are extremely wear resistant, but
relatively brittle. Once a crack starts, it can propagate through the
compact and eventually result in failure of the part. This is particularly
true in the case of petroleum or rock drill bits, in which a massive
failure of the diamond layer of an insert made of a polycrystalline
diamond compact can lead to damage of the other cutters on the bit or the
bit body.
Additionally, diamond or CBN compacts are relatively expensive to
manufacture with the high pressure/high temperature process. Further, the
size of the diamond or CBN compacts is limited by the dimensions of the
press cell. Typically, only a few pieces, each having a cross-section of
less than 1 inch, can be processed in a press cell, while the largest
piece that presently can be processed has a cross-section of less than 2
inches.
For the foregoing reasons, there exists a need for a wear-resistant
material that utilizes the wear resistance of diamond or CBN materials
while possessing a higher toughness than previously typical of diamond or
CBN compacts. Further, it is desirable that the method of manufacturing
such a composite material be capable of producing parts that are larger
than 2 inches in cross-section.
SUMMARY OF INVENTION
In some aspects the invention relates to a super-hard composite material
comprising: a super-hard component representing about 40%-85% of the
volume of the super-hard material; a metal matrix component representing
about 15%-60% of the volume of the super-hard material; and wherein the
super-hard component and the metal matrix component are combined in a
uniform composite mixture with an actual density at least 95% of the
theoretical maximum density of the composite mixture.
In an alternative embodiment, the invention relates to a method for
manufacturing a super-hard composite material comprising: providing a
super-hard component representing about 40%-85% of the volume of the
super-hard composite material; providing a metal matrix component
representing about 15%-60% of the volume of the super-hard composite
material; milling the super-hard component with the metal matrix component
to achieve a uniform mixture; and compacting the uniform mixture to an
actual density at least 95% of the theoretical maximum density of the
mixture.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1a shows a schematic of a typical rapid omni-directional compaction
process before compaction.
FIG. 1b shows a schematic of a typical rapid omni-directional compaction
process before compaction.
FIG. 2 is a rock bit manufactured in accordance with an embodiment of the
invention.
DETAILED DESCRIPTION
Exemplary embodiments of the invention will be described with reference to
the accompanying drawings. Like items in the drawings are shown with the
same reference numbers.
Embodiments of the invention provide a metal-matrix/super-hard composite
that exhibits a higher toughness than currently available diamond or CBN
compacts while maintaining superior wear resistance. Such
metal-matrix/super-hard composites contain super-hard grains that are
dispersed uniformly in a metal matrix such as cobalt, nickel, iron, or
alloys thereof. Suitable super-hard materials include diamond and cubic
boron nitride. The microstructure of the composites is such that the
composite is substantially free of large clusters of grains of the
super-hard material. The grain-to-grain contiguity of the super-hard
material is less than 40%, and the average size of the matrix metal pools
in the composite is smaller than the average size of the grains of the
super-hard material.
Although embodiments of the invention include both diamond and boron
nitride as the super-hard material, metal-matrix/diamond composites are
exemplified and explained in more detail than metal-matrix/CBN composites.
However, it should be understood that any such descriptions are similarly
applicable to metal-matrix/CBN composites.
In preferred embodiments, each diamond grain is surrounded by cobalt, which
acts as a matrix. The super-hard, brittle diamond grains thus are embedded
in a matrix of a relatively ductile metal. The ductile metal matrix
provides the necessary toughness, while the grains of super-hard material
in the matrix furnish the necessary wear resistance. The grains of
super-hard material perform the cutting function while being held in place
by the relatively ductile metal matrix. The ductile metal matrix also
reduces crack formation and suppresses crack propagation through the
composite material once a crack has been initiated. As a result of this
combination of super-hard material grains surrounded by a metal matrix,
these composites possess higher toughness but still maintain superior wear
resistance as compared to conventional diamond or CBN compacts.
The metal-matrix/diamond or metal-matrix/CBN composites of the present
invention may be manufactured by the following method: (1) milling a
mixture of diamond or CBN grains and one or more metal powders to form a
uniform mixture; and (2) hot-compacting the mixture to an actual density
that is at least 95% of the theoretical maximum density of the mixture. It
should be understood that, in a powder mixture, there typically is a
certain degree of porosity. The theoretical maximum density of a mixture
refers to the density of such a mixture with zero porosity.
In some embodiments, the mixture includes between 40% to 85% by volume of
diamond grains and correspondingly between 15% to 60% by volume of metal
matrix material. It should be recognized that it is possible to obtain a
mixture that contains between 1% to 99% by volume of diamond or CBN grains
according to embodiments of the invention.
The diamond grains used in the embodiments may either be natural or
synthetic diamond grit. Although it is possible to use diamond grains of
any size, it is preferred that the average grain size of diamond falls in
the range of between 1 .mu.m and 30 .mu.m.
In some embodiments, the super-hard grains are coated with a metal layer
before milling to prevent surface oxidation of the super-hard material
during the hot-compaction process. While copper is a suitable material for
such a coating, other materials, such as titanium nitride, titanium
carbonitride, zirconium nitride, cobalt, tungsten, and nickel, also may be
used.
Sometimes it is desirable to heat-treat the diamond grains in a hydrogen
atmosphere at an elevated temperature. Typically, the temperature range is
from 600.degree. C. to 1200.degree. C. It is believed that the hydrogen
treatment step facilitates the removal of oxygen-containing species on the
surface of the diamond grains. This tends to reduce the extent of
oxidation of the diamond grains in the subsequent hot-compaction process.
This step may be done either before or after the milling of the grains and
the powder.
Suitable metal powders that may be mixed with diamond grains include
nickel, iron, cobalt, and mixtures or alloys thereof. Suitable metals also
may include Mo, W, Ti, Nb, Ta, V, other transitional metals, and their
alloys. In a preferred embodiment, cobalt powder is used to form the metal
matrix. Although the particle size of the cobalt powder may be in any
range, it is preferred that the average cobalt powder particle size falls
within a range between 1 .mu.m and 30 .mu.m.
The cobalt powder and diamond grains are milled together to form a mixture
where the diamond grains are uniformly distributed in the cobalt powder.
Such uniformity may be indicated by diamond grain-to-grain contiguity,
although other parameters also are acceptable. Any powder milling
technique that renders a uniform mixing can be used. In a preferred
embodiment, attritor-milling was employed at 300 rpm for two hours to
obtain a uniform mixture.
After a uniform mixture of diamond grains and cobalt powder is obtained, a
cold-compacted "green" piece of a desired shape is made from the mixture.
The green piece then is subjected to a hot-compaction process to achieve
an actual density that is at least 95% of the theoretical maximum density.
Suitable methods of hot compaction may include hot isostatic pressing, hot
pressing, rapid omni-directional compaction, and a high pressure/high
temperature process. Although it is preferred that a hot-compaction
process be used to obtain the desired density, it should be understood
that any compaction process, including cold-compaction, may be utilized.
Further, it should be recognized that compaction to an actual density to
less than 95% of the theoretical maximum density may be acceptable for
some applications.
In a preferred embodiment, the rapid omni-directional compaction process is
used to make the composites because it operates at a lower pressure than
the HPHT process. Additionally, it provides excellent dimensional control.
This makes it an ideal near-net shape production method with mechanical
properties at least equal to or better than those produced by hot
isostatic pressing. Another advantage is higher production output and
lower production cost than other processes. Also, when compared to the
HPHT process, the rapid omni-directional compaction process can produce
substantially larger work pieces. Finally, the relatively short thermal
exposure given to the powders during rapid omni-directional compaction
results in retention of a very fine microstructure with excellent
mechanical properties. The rapid omni-directional compaction process has
been described in U.S. Pat. No. 4,428,906 and No. 4,656,002, and the
teachings of these patents are incorporated by reference herein.
FIG. 1 illustrates a typical rapid omni-directional compaction apparatus
that is used in some embodiments. A forging press 20 commonly is employed
in a rapid omni-directional compaction process. It includes a ram 10, a
pot die 12, and a fluid die 22. There is a close fit between the ram 10
and the fluid die 22. Inside the fluid die 22 there is a
pressure-transmitting medium 16. The pressure-transmitting medium may be
made from various materials that melt at a lower temperature than the
temperatures used during compaction. In some embodiments, the pre-pressed
diamond/metal powder mixture 14 is surrounded by a non-reactive insulation
layer 15 to prevent contact between the molten medium 16 and the powder
mixture 14.
As the ram 10 travels downward, the powder mixture 14 is pressed from all
directions, resulting in a metal-matrix/diamond composite 18. Complete
consolidation in the inter-particle bonding is accomplished, without
pressure dwell, in a single ram stroke that produces pressures in the
range of approximately 345 to 895 MPa (50 to 130 ksi). A typical
consolidation temperature is between about 800.degree. C. and 1500.degree.
C., although other temperature ranges also are acceptable. In a preferred
embodiment, the diamond/metal powder mixture is compressed to 120 ksi at
1200.degree. C. for about two minutes.
In addition to the rapid omni-directional compaction process, the HPHT
process for sintering diamond or cubic boron nitride may be used. Such a
process has been described in U.S. Pat. No. 5,676,496 and No. 5,598,621
and their teachings are incorporated by reference herein. Another suitable
method for hot-compacting pre-pressed diamond/metal powder mixtures is hot
isostatic pressing, which is known in the art. See Peter E. Price and
Steven P. Kohler, "Hot Isostatic Pressing of Metal Powders", Metals
Handbook, Vol. 7, pp. 419-443 (9th ed. 1984).
The metal-matrix diamond or cubic boron nitride composites made in
accordance with embodiments of the invention may be used as blanks for
cutting tools, drill bits, dressing tools, and wear parts. Further, the
metal-matrix diamond or cubic boron nitride composites that are made in a
cylindrical configuration may also be used to make wire drawing dies. An
example of a rock bit for downhole drilling constructed in accordance with
embodiments of the invention is illustrated in FIG. 2. An rock bit 30
includes a bit body 40 with a threaded section 34 on its upper end for
securing the bit to a drill string (not shown). The bit 30 generally has
three roller cones 36 rotatably mounted on bearing shafts (hidden) that
depend from the bit body 40. The bit body 40 comprises three sections or
legs 42 (two legs are shown) that are welded together to form the bit body
40. The bit 30 further includes a plurality of nozzles 45 that are
provided for directing drilling fluid toward the bottom of a borehole and
around the roller cones 36. In addition, the bit 30 also may include
lubricant reservoirs 44 that supply lubricant to the bearings of each of
the roller cones.
Generally, each roller cone 36 includes a frustoconical surface 37 that is
adapted to retain inserts that scrape or ream the sidewalls of a borehole
as the roller cones 36 rotate about the borehole bottom. The frustoconical
surface 37 will be referred to herein as the "heel" surface of the roller
cones 36, although the same surface may be sometimes referred to in the
art as the "gage" surface of the roller cone.
The roller cone 36 includes a plurality of heel row inserts 50 that are
secured in a circumferential row in the frtustoconical heel surface 37.
The roller cone 36 further includes a circumferential row of gage inserts
35 secured in locations along or near the circumferential shoulder 39.
Also, the roller cone 36 includes a plurality of inner row inserts 38 that
are secured to the roller cone surface and arranged in respective rows.
Although various geometric shapes of the inserts are acceptable, it is
preferred that they have a semi-round top, a conical top, or a chiseled
top.
The inserts include generally cylindrical base portions that are secured by
an interference fit into mating sockets drilled into the lands of the cone
cutter and cutting portions that are connected to the base portions. The
cutting portion includes a cutting surface that extends from the surface
of the roller cone for cutting or crushing the rock formation being
drilled.
In accordance with embodiments of the invention, the metal-matrix/diamond
or metal-matrix/CBN composites may be manufactured in the form of inserts
for use in rock bits. Rock bits incorporating inserts made of these
composites have a longer bit life and a higher rate of penetration.
Preferably, the composites are used for making gage row inserts and heel
row inserts, although it is conceivable that they also may be used to make
inner row inserts. In addition to forming an insert, the composites also
may be used to replace the diamond layer in diamond-enhanced inserts.
Examples of such diamond-enhanced inserts are described in U.S. Pat. No.
4,006,788 and No. 4,972,912, and the teachings of these patents are
incorporated by reference herein.
As described above, embodiments of the invention provide a
metal-matrix/diamond or metal-matrix/CBN composite that is tougher than
polycrystalline diamond or CBN compacts manufactured by the high
pressure/high temperature sintering process. The metal-matrix/diamond or
metal-matrix/CBN composite has a very fine microstructure in which grains
of diamond or CBN generally are uniformly distributed in a metal matrix.
Such a fine microstructure results in a higher fracture toughness than
conventional polycrystalline diamond or CBN compacts. In addition, the
hot-compaction process may be carried out at a lower pressure than the
traditional HPHT sintering process, thereby reducing production costs.
Moreover, it is possible to manufacture parts made of the
metal-matrix/diamond or metal-matrix/CBN composite having dimensions
larger than those currently available using the traditional HPHT sintering
process.
While the invention has been disclosed with respect to a limited number of
embodiments, numerous modifications and variations therefrom are possible.
For example, suitable super-hard grains are not limited to diamond, CBN,
and mixtures thereof. Other super-hard materials, such as ceramics,
cermets, nitrides, and carbides, also may be used. Particles of
diamond-like carbon also may be used. With respect to suitable metals for
the metal matrix, any suitable metal or alloys may be used. It is intended
that the appended claims cover all such modifications and variations as
fall within the true spirit and scope of the invention.
While the invention has been disclosed with reference to specific examples
of embodiments, numerous variations and modifications are possible.
Therefore, it is intended that the invention not be limited by the
description in the specification, but rather the claims that follow.
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